draft-ietf-dhc-userclass-00.txt   draft-ietf-dhc-userclass-01.txt 
Network Working Group Glenn Stump, IBM Network Working Group Glenn Stump, IBM
INTERNET DRAFT Ralph Droms, Bucknell University INTERNET DRAFT Ralph Droms, Bucknell University
November 1996 March 1997
Expires May 1996 Expires September 1997
The User Class Option for DHCP The User Class Option for DHCP
<draft-ietf-dhc-userclass-00.txt> <draft-ietf-dhc-userclass-01.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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Throughout this document, the words that are used to define the Throughout this document, the words that are used to define the
significance of particular requirements are capitalized. These words significance of particular requirements are capitalized. These words
are: are:
o "MUST" o "MUST"
This word or the adjective "REQUIRED" means that the This word or the adjective "REQUIRED" means that the
item is an absolute requirement of this specification. item is an absolute requirement of this specification.
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o "MUST NOT" o "MUST NOT"
This phrase means that the item is an absolute prohibition This phrase means that the item is an absolute prohibition
of this specification. of this specification.
o "SHOULD" o "SHOULD"
This word or the adjective "RECOMMENDED" means that there This word or the adjective "RECOMMENDED" means that there
may exist valid reasons in particular circumstances to ignore may exist valid reasons in particular circumstances to ignore
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A DHCP server of "server"is an Internet host that returns A DHCP server of "server"is an Internet host that returns
configuration parameters to DHCP clients. configuration parameters to DHCP clients.
o "binding" o "binding"
A binding is a collection of configuration parameters, including A binding is a collection of configuration parameters, including
at least an IP address, associated with or "bound to" a DHCP at least an IP address, associated with or "bound to" a DHCP
client. Bindings are managed by DHCP servers. client. Bindings are managed by DHCP servers.
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3. User Class Information 3. User Class Information
This option is used by a DHCP client to optionally identify the type This option is used by a DHCP client to optionally identify the type
or category of user or applications it represents. The information or category of user or applications it represents. The information
contained in this option is an NVT ASCII text object that represents contained in this option is an NVT ASCII text object that represents
the user class of which the client is a member. the user class of which the client is a member.
DHCP administrators may define specific user class identifiers to DHCP administrators may define specific user class identifiers to
convey information about a client's software configuration or about convey information about a client's software configuration or about
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(and may announce they are doing so) in a degraded mode. (and may announce they are doing so) in a degraded mode.
The code for this option is 77. The minimum length for this option The code for this option is 77. The minimum length for this option
is two. is two.
Code Len text1 Code Len text1
+-----+-----+-----+-----+----- +-----+-----+-----+-----+-----
| 77 | N | c1 | c2 | ... | 77 | N | c1 | c2 | ...
+-----+-----+-----+-----+----- +-----+-----+-----+-----+-----
Implemention Note: Simulating Multiple User Classes
Although the user class option field only permits one NVT string, the
working group envisions that multiple classes can be simulated by
creating combination classes which map into a single class NVT
string. For example, suppose a site desires to create multiple
logical user classes, including:
"mobile" -- These hosts receive short lease times
and are assumed to dynamically update
their own DNS records
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"engineer" -- These hosts are assigned a high-
performance NFS file server
For the above two classes, then, a combination class could look
something like:
"mobeng" -- hosts of this mobile-engineer combination
class get assigned a high-performance
file server and a short lease time, and
a DNS proxy A record update is not attempted
on their behalf.
Thus, by mapping combinations of classes into single class names, you
can effectively implement multiple user classing at a site using only
the single NVT string field.
Implementation Note: Serving Competing Option Values
When servicing a request from a client of a particular user class, a
DHCP server makes decisions about what collection of options to
include in its response. These decisions are expected to consider
options and values designated for the client host by virtue of its
subnet/location, vendor class, user class, or client id.
In cases where multiple option values are possible for return to the
client due to multiple, overlapping "affiliations", DHCP server
policy may dictate which values take precedence over others. A DHCP
server implementation SHOULD provide flexibility in specifying DHCP
option precedence policy so that DHCP administrators can customize a
DHCP system to best suit their network environments.
If flexibility in a server's option precedence policy is not
implemented by a vendor (or is perhaps implemented but not exercised
by an administrator), a recommended default policy is that option
values of specific affiliations override those of less specific.
That is, an option value designated for a specific client --
sometimes known as a "reserved binding" -- SHOULD override option
values designated for the client's user or vendor class, which SHOULD
override option values designated for the client's vendor class,
which SHOULD override option values for the client's subnet.
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Security Considerations Security Considerations
Security issues are not discussed in this document. Security issues are not discussed in this document.
References References
[DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC1541, [DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC1541,
October 1993 October 1993
Acknowledgments Acknowledgments
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Author Information Author Information
Glenn Stump Glenn Stump
IBM Networking Software Solutions IBM Networking Software Solutions
4205 South Miami Blvd. 4205 South Miami Blvd.
RTP, NC 27709 RTP, NC 27709
Phone: (919) 254-5616 Phone: (919) 254-5616
email: glennstump@vnet.ibm.com email: glennstump@vnet.ibm.com
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